Fluid heat exchanger

ABSTRACT

A fluid heat exchanger includes: a heat spreader plate including an intended heat generating component contact region; a plurality of microchannels for directing heat transfer fluid over the heat spreader plate, the plurality of microchannels each having a first end and an opposite end and each of the plurality of microchannels extending substantially parallel with each other microchannel and each of the plurality of microchannels having a continuous channel flow path between their first end and their opposite end; a fluid inlet opening for the plurality of microchannels and positioned between the microchannel first and opposite ends, a first fluid outlet opening from the plurality of microchannels at each of the microchannel first ends; and an opposite fluid outlet opening from the plurality of microchannels at each of the microchannel opposite ends, the fluid inlet opening and the first and opposite fluid outlet openings providing that any flow of heat transfer fluid that passes into the plurality of microchannels, flows along the full length of each of the plurality of microchannels in two directions outwardly from the fluid inlet opening. A method of cooling a heat generating component uses a fluid heat exchanger that splits a mass flow of coolant.

FIELD

The present invention is directed to a fluid heat exchanger and, inparticular, a fluid heat exchanger for an electronics application suchas in a computer system.

BACKGROUND

Fluid heat exchangers are used to cool electronic devices by acceptingand dissipating thermal energy therefrom.

Fluid heat exchangers seek to dissipate to a fluid passing therethrough,thermal energy communicated to them from a heat source.

SUMMARY

In accordance with a broad aspect of the invention, there is provided afluid heat exchanger comprising: a heat spreader plate including anintended heat generating component contact region; a plurality ofmicrochannels for directing heat transfer fluid over the heat spreaderplate, the plurality of microchannels each having a first end and anopposite end and each of the plurality of microchannels extendingsubstantially parallel with each other microchannel and each of theplurality of microchannels having a continuous channel flow path betweentheir first end and their opposite end; a fluid inlet opening for theplurality of microchannels and positioned between the microchannel firstand opposite ends, a first fluid outlet opening from the plurality ofmicrochannels at each of the microchannel first ends; and an oppositefluid outlet opening from the plurality of microchannels at each of themicrochannel opposite ends, the fluid inlet opening and the first andopposite fluid outlet openings providing that any flow of heat transferfluid that passes into the plurality of microchannels, flows along thefull length of each of the plurality of microchannels in two directionsoutwardly from the fluid inlet opening.

In accordance with another broad aspect of the present invention, thereis provided a method for cooling a heat generating component comprising:providing a fluid heat exchanger including a heat spreader plate; aplurality of microchannels for directing heat transfer fluid over theheat spreader plate, the plurality of microchannels each having a firstend and an opposite end and each of the plurality of microchannelshaving a continuous channel flow path between their first ends and theiropposite ends; a fluid inlet opening for the plurality of microchannelsand positioned between the microchannel first and opposite ends, a firstfluid outlet opening from the plurality of microchannels at each of themicrochannel first ends; and an opposite fluid outlet opening from theplurality of microchannels at each of the microchannel opposite ends;mounting the heat spreader plate onto the heat generating componentcreating a heat generating component contact region where the heatgenerating component contacts the heat spreader plate; introducing aflow of heat exchanging fluid to the fluid heat exchanger; urging theflow of heat exchanging fluid through the fluid inlet into the pluralityof microchannels first to a microchannel region between the ends of themicrochannel; and, diverting the flow of heat exchanging fluid into aplurality of subflows that each flow away from the other, a first of theplurality of subflows flowing from the fluid inlet toward the firstfluid outlet and a second of the plurality of subflows flowing from thefluid inlet toward the opposite fluid outlet.

It is to be understood that other aspects of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein various embodiments of the invention areshown and described by way of illustration. As will be realized, theinvention is capable for other and different embodiments and its severaldetails are capable of modification in various other respects, allwithout departing from the spirit and scope of the present invention.

Accordingly the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings wherein like reference numerals indicatesimilar parts throughout the several views, several aspects of thepresent invention are illustrated by way of example, and not by way oflimitation, in detail in the figures, wherein:

FIG. 1 is a top plan view of a fluid heat exchanger according to oneembodiment of the invention, with the top cap cut away to facilitateviewing internal components;

FIG. 2 is a sectional view along line I-I of FIG. 1;

FIG. 3 is a sectional view along line II-II of FIG. 2;

FIG. 4 is an exploded, perspective view of a fluid heat exchangeraccording to another embodiment of the invention; and

FIG. 5 is a top plan view of the fluid heat exchanger of FIG. 4assembled with its top cap removed.

DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various embodiments of thepresent invention and is not intended to represent the only embodimentscontemplated by the inventor. The detailed description includes specificdetails for the purpose of providing a comprehensive understanding ofthe present invention. However, it will be apparent to those skilled inthe art that the present invention may be practiced without thesespecific details.

With reference to FIGS. 1 to 3, a fluid heat exchanger 100 is shown.Fluid heat exchanger 100 includes a heat spreader plate 102, anarrangement of fluid microchannels 103 defined between walls 110, afluid inlet passage 104, and a fluid outlet passage 106. A housing 109operates with heat spreader plate 102 to form an outer limit of the heatsink and to define fluid flow passages 104, 106.

As shown in FIGS. 2 and 3, in use the heat exchanger 100 is coupled to aheat source 107, such as an electronic device, including, but notlimited to a microchip or an integrated circuit. The heat exchanger maybe thermally coupled to the heat source by a thermal interface materialdisposed therebetween, by coupling directly to the surface of the heatsource, or by integrally forming the heat source and at least the heatspreader plate 102 of the fluid heat exchanger. The heat exchanger 100may take various forms and shapes, but heat spreader plate 102 is formedto accept thermal energy from heat source 107. Heat spreader plate 102includes an intended heat generating component contact region 102 bpositioned in a known location thereon. In the illustrated embodiment,heat spreader plate 102 includes a protrusion at region 102 b thatcontrols the positioning of the heat spreader plate relative to the heatsource, but such a protrusion need not be included. Heat spreader plate102 may include a portion of more conductive material to facilitate andcontrol heat transfer, if desired. In any event, heat spreader plate isformed to fit over and thermally communicate with a heat source in aregion 102 b, usually located centrally relative to the edges of theheat spreader plate.

Microchannels 103 are formed to accept and allow passage therethrough ofthe flow of heat exchanging fluid such that the fluid can move alongheat spreader plate 102 and walls 110 and accept and dissipate heatenergy from them. In the illustrated embodiment, microchannels 103 aredefined by walls 110 that are thermally coupled to the heat spreaderplate to accept thermal energy therefrom. For example, heat spreaderplate 102 may include an inner facing, upper surface 102 a and aplurality of microchannel walls 110 may extend upwardly therefrom,whereby the channel area, defined between upper surface 102 a and themicrochannel walls 110, channels or directs fluid to create a fluid flowpath. The channel area may be open or filled with thermally conductiveporous material such as metal or silicon foam, sintered metal, etc.Thermally conductive, porous materials allow flow through the channelsbut create a tortuous flow path.

Surface 102 a and microchannel walls 110 allow the fluid to undergoexchange of thermal energy from the heat spreader plate to cool the heatsource coupled to the heat spreader plate. The upper surface 102 a andwalls 110 have a high thermal conductivity to allow heat transfer fromthe heat source 107 to fluid passing through channels 103. The surfacesforming channels 103 may be smooth and solid, formed with a porousstructure, such as of sintered metal and/or metal or silicon foam orroughened, for example, including troughs and/or crests designed tocollect or repel fluid from a particular location or to create selectedfluid flow properties. Facing microchannel walls 110 may be configuredin a parallel configuration, as shown, or may be formed otherwise,provided fluid can flow between the microchannel walls 110 along a fluidpath. It will be apparent to one skilled in the art that themicrochannel walls 110 may be alternatively configured in any otherappropriate configuration depending on various factors of desired flow,thermal exchange, etc. For instance, grooves may be formed betweensections of microchannel walls 110. Generally, microchannel walls 110may desirably have dimensions and properties which seek to reduce orpossibly minimize the pressure drop or differential of fluid flowingthrough the channels 103 defined therebetween.

The microchannel walls 110 may have a width dimension within the rangeof 20 microns to 1 millimeter and a height dimension within the range of100 microns to five millimeters, depending on the power of the heatsource 107, desired cooling effect, etc. The microchannel walls 110 mayhave a length dimension which ranges between 100 microns and severalcentimeters, depending on the dimensions of, and the heat flux densityfrom, the heat source. In one embodiment, the walls 110 extend the fulllength (which may be a width) dimension of the heat spreader platepassing fully through region 102 b. These are exemplary dimensions and,of course, other microchannel wall dimensions are possible. Themicrochannel walls 110 may be spaced apart by a separation dimensionrange of 20 microns to 1 millimeter, depending on the power of the heatsource 107, although other separation dimensions are contemplated.

Other microporous channel configurations may be used alternatively to,or together with, microchannels, such as for example, a series ofpillars, fins, or undulations, etc. which extend upwards from the heatspreader plate upper surface or tortuous channels as formed by a foam orsintered surface.

Fluid heat exchanger 100 further includes a fluid inlet passage 104,which in the illustrated embodiment includes a port 111 through thehousing opening to a header 112 and thereafter a fluid inlet opening 114to the microporous fluid channels 103.

The port and the header can be formed in various ways andconfigurations. For example, port 111 may be positioned on top, asshown, side or end regions of the heat exchanger, as desired. Port 111and header 112 are generally of a larger cross sectional area thanopening 114, so that a mass flow of fluid can be communicatedsubstantially without restriction to opening 114.

Although only a single fluid inlet opening 114 is shown, there may beone or more fluid inlet openings providing communication from the headerto the fluid microchannels 103.

Fluid inlet opening 114 may open to microchannels 103 opposite the heatspreader plate such that fluid passing through the opening may passbetween walls 110 toward surface 102 a, before being diverted along theaxial length of the channels, which extend parallel to axis x. Sincemost installations will position the heat spreader plate as thelowermost, as determined by gravity, component of heat exchanger 100,the fluid inlet openings 114 can generally be described as beingpositioned above the microchannels 103 such that fluid may flow throughopening 114 down into the channels in a direction orthogonal relative tothe plane of surface 102 a and towards surface 102 a and then changedirection to pass along the lengths of channels 103 substantiallyparallel to surface 102 a and axis x. Such direction change is driven byimpingement of fluid against surface 102 a.

Fluid inlet opening 114 may be positioned adjacent to the known intendedheat generating component contact region 102 b since this region of theheat spreader plate may be exposed to greater inputs of thermal energythan other regions on plate 102. Positioning the fluid inlet openingadjacent region 102 b seeks to introduce fresh heat exchanging fluidfirst and directly to the hottest region of the heat exchanger. Theposition, arrangement and/or dimensions of opening 114 may be determinedwith consideration of the position of region 102 b such that opening 114may be placed adjacent, for example orthogonally opposite to, oraccording to the usual mounting configuration above, the intended heatgenerating component contact region 102 b on the heat plate. Thedelivery of fresh fluid first to the region that is in directcommunication with the heat generating component to be cooled seeks tocreate a uniform temperature at the contact region as well as areas inthe heat spreader plate away from the contact region.

In the illustrated embodiment, opening 114 is positioned to have itsgeometric center aligned over the center, for example the geometriccenter, of region 102 b. It is noted that it may facilitate constructionand installation by intending, and possibly forming, the heat sinkspreader plate to be installed with the heat generating componentpositioned on the plate substantially centrally, with respect to theplate's perimeter edges, and then opening 114 may be positioned alsowith its geometric center substantially centrally with respect to theperimeter edges of the heat spreader plate. In this way, the geometriccenter points of each of opening 114, the heat spreader plate and theheat generating component may all be substantially aligned, as at C.

Opening 114 may extend over any channel 103 through which it is desiredthat heat exchange fluid flows. Openings 114 may take various formsincluding, for example, various shapes, various widths, straight orcurved edges (in plane or in section) to provide fluid flow features,open area, etc., as desired.

Heat exchanger 100 further includes a fluid outlet passage 106, which inthe illustrated embodiment includes one or more fluid outlet openings124 from the microporous fluid channels 103, a header 126 and an outletport 128 opening from the housing. Although two fluid outlet openings124 are shown, there may be one or more fluid outlet openings providingcommunication to the header from the fluid channels 103.

The port and the header can be formed in various ways andconfigurations. For example, port 128 may be positioned on top, asshown, side or end regions of the heat exchanger, as desired.

Fluid outlet openings 124 may be positioned at the end of microchannels103. Alternately or in addition, as shown, fluid outlet openings 124 maycreate an opening opposite heat spreader plate 102 such that fluidpassing through the channels pass axially along the length of thechannels between walls 110 and then changes direction to pass away fromsurface 102 a out from between the walls 110 to exit through openings124. Since most installations will position the heat spreader plate asthe lowermost, as determined by gravity, component of heat exchanger100, the fluid outlet openings 124 will generally be positioned abovethe microchannels 103 such that fluid may flow from the channelsupwardly through openings 124.

Fluid outlet openings 124 may be spaced from fluid inlet openings 114 sothat fluid is forced to pass through at least a portion of the length ofchannels 103 where heat exchange occurs before exiting themicrochannels. Generally, fluid outlet openings 124 may be spaced fromthe known intended heat generating component contact region 102 b.

In the illustrated embodiment, where heat exchanger 100 is intended tobe mounted with heat source 107 generally centrally positioned relativeto the perimeter edges of heat spreader plate 102, and thereby the ends103 a of channels, openings 124 may be positioned at or adjacent channelends 103 a.

At least one opening 124 extends over any channel 103 through which itis desired that heat exchange fluid flows. Openings 124 may take variousforms including, for example, various shapes, various widths, straightor curved edges (in plane or in section) to provide fluid flow features,open area, etc. as desired.

Fluid inlet opening 114 may open away from the ends of themicrochannels, for example along a length of a microchannel between itsends. In this way, fluid is introduced to a middle region of acontinuous channel 103 rather than fluid being introduced to one end ofa channel and allowing it to flow the entire length of the channel. Inthe illustrated embodiment, heat exchanger 100 is intended to be mountedwith heat source 107 generally centrally positioned relative to theperimeter edges of heat spreader plate 102. As such, in the illustratedembodiment, opening 114 is positioned generally centrally relative tothe edges of the heat plate 102. Since the channels, in the illustratedembodiment extend substantially continuously along the length of theheat plate between opposing side perimeter edges thereof, opening 114opens generally centrally between ends 103 a of each channel. Forexample, opening 114 may be positioned in the middle 50% of the heatexchanger or possibly the middle 20% of the heat exchanger. The deliveryof fresh fluid to the central region where the heat generating componentis in direct communication with the heat spreader plate, first beforepassing through the remaining lengths of channels seeks to create auniform temperature at region 102 b as well as areas in the heatspreader plate adjacent to the intended mounting position. Theintroduction of fluid to a region along a middle region of themicrochannels after which the flow splits into two sub flows to passoutwardly from the inlet towards a pair of outlets, each of which ispositioned at the ends of the channels reduces the pressure drop offluid passing along the channels over that pressure drop that would becreated if the fluid passed along the entire length of each channel.Splitting the fluid flow to allow only approximately one half of themass inlet flow to pass along any particular region of the microchannelscreates less back pressure and less flow resistance, allows faster fluidflow through the channels and lessens the pump force required to movethe fluid through the heat exchanger.

In use, heat spreader plate 102 is positioned in thermal communicationwith heat source 107 at region 102 b. Heat generated by heat source 107is conducted up through heat spreader plate 102 to surface 102 a andwalls 110. Heat exchanging fluid, as shown by arrows F, enters the fluidheat exchanger through port 111, passes into the header 112 and throughopening 114. The heat exchanging fluid then passes down between walls110 into channels 103, where the fluid accepts thermal energy from thewalls 110 and surface 102 a. The heat exchanging fluid, after passingdown into the channels, then impinges against surface 102 a to bediverted toward ends 103 a of the channels toward outlet openings 124.In so doing, in the illustrated embodiment, the fluid is generally splitinto two subflows moving away from each other and away from inlet 114toward openings 124 at the ends of the microchannels. Fluid passingthrough channels becomes heated, especially when passing over the regionin direct contact with the heat source, such as, in the illustratedembodiment, the central region of the heat spreader plate. Heated fluidpasses out of openings 124, into header and thereafter through port 128.The heated fluid will circulate through a heat sink where its thermalenergy is unloaded before circulating back to port 111.

The individual and relative positioning and sizing of openings 114 and124 may allow fluid to circulate through the heat exchanging channels103 while reducing the pressure drop generated in fluid passing throughheat exchanger 100, when compared to other positionings and sizings. Inthe illustrated embodiment, for example, the central region 124 a ofoutlet openings 124 are scalloped to offer an enlarged outlet regionfrom the centrally located channels, relative to those on the edges.This shaping provides that the outlet openings from some centrallypositioned channels 103, relative to the sides of the heat exchanger,are larger than the outlet openings from other channels closer to theedges. This provides that fluid flowing through the more centrallylocated channels encounters less resistance to flow therethrough, againfacilitating flow past the central mounting region 102 b on heatspreader plate 102.

A seal 130 separates fluid inlet passage 104 from fluid outlet passage106 so that fluid must pass through the microporous channels 103 pastheat spreader plate surface 102 a.

With reference to FIGS. 4 and 5, a useful method for manufacturing afluid heat exchanger is described. A heat spreader plate 202 may beprovided which has heat conductive properties through its thickness atleast about a central region thereof.

Microchannels may be formed on the surface of the heat spreader plate,as by adding walls or forming walls by building up or removing materialsfrom the surface of the heat plate. In one embodiment, skiving is usedto form walls 210.

A plate 240 may be installed over the walls 210 to close off thechannels across the upper limits of walls 210. Plate 240 has portionsremoved to create inlet and outlet openings 214 and 224, respectively,in the final heat exchanger. Tabs 242 may be used to assist with thepositioning and installation of plate 240, wherein tabs 242 are bentdown over the two outermost walls.

Seal 230 may be installed as a portion of plate 240 or separately.

After plate 240 and seal 230 are positioned, a top cap 244 can beinstalled over the assembly. Top cap 244 can include side walls thatextend down to a position adjacent heat spreader plate. The parts may beconnected during assembly thereof or afterward by overall fusingtechniques. In so doing, the parts are connected so that shortcircuiting from inlet passage to outlet passage is substantiallyavoided, setting up the fluid circuit as described herein above whereinthe fluid flows from opening 214 to openings 224 through the channelsdefined between walls 210.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to those embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the full scope consistent with the claims, wherein reference toan element in the singular, such as by use of the article “a” or “an” isnot intended to mean “one and only one” unless specifically so stated,but rather “one or more”. All structural and functional equivalents tothe elements of the various embodiments described throughout thedisclosure that are know or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the elements of theclaims. Moreover, nothing disclosed herein is intended to be dedicatedto the public regardless of whether such disclosure is explicitlyrecited in the claims. No claim element is to be construed under theprovisions of 35 USC 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for” or “step for”.

1. A fluid heat exchanger comprising: a heat spreader plate including anintended heat generating component contact region; a plurality ofmicrochannels for directing heat transfer fluid over the heat spreaderplate, the plurality of microchannels each having a first end and anopposite end and each of the plurality of microchannels extendingsubstantially parallel with each other microchannel and each of theplurality of microchannels having a continuous channel flow path betweentheir first end and their opposite end; a fluid inlet opening for theplurality of microchannels and positioned between the microchannel firstand opposite ends, a first fluid outlet opening from the plurality ofmicrochannels at each of the microchannel first ends; and an oppositefluid outlet opening from the plurality of microchannels at each of themicrochannel opposite ends, the fluid inlet opening and the first andopposite fluid outlet openings providing that any flow of heat transferfluid that passes into the plurality of microchannels, flows along thefull length of each of the plurality of microchannels in two directionsoutwardly from the fluid inlet opening.
 2. The fluid heat exchanger ofclaim 1 wherein the fluid inlet opening is positioned in the middle 50%of a length measured between the microchannel first ends and themicrochannel opposite ends.
 3. The fluid heat exchanger of claim 1wherein the fluid inlet opening is positioned in the middle 20% of alength measured between the microchannel first ends and the microchannelopposite ends.
 4. The fluid heat exchanger of claim 1 wherein theintended heat generating component contact region is in a known locationon the heat spreader plate and the fluid inlet opening is positionedadjacent a central region of the intended heat generating componentcontact region.
 5. The fluid heat exchanger of claim 1 wherein the heatspreader plate includes perimeter edges and a length measuredtherebetween from perimeter edge to perimeter edge, and wherein theplurality of microchannels extend substantially the length of the heatspreader plate.
 6. The fluid heat exchanger of claim 1 wherein the fluidinlet is positioned opposite the heat spreader plate such that fluidpassing through the fluid inlet into the plurality of microchannelsmoves orthogonally relative to the plane of and toward the heat spreaderplate.
 7. The fluid heat exchanger of claim 1 wherein the first fluidoutlet is positioned opposite the heat spreader plate such that fluidpassing from the plurality of microchannels through the first fluidoutlet moves orthogonally relative to and away from the heat spreaderplate.
 8. The fluid heat exchanger of claim 1 wherein the fluid inletopens into all of the plurality of microchannels positioned on the heatspreader plate.
 9. The fluid heat exchanger of claim 1 wherein theplurality of microchannels includes a first microchannel passing overthe intended heat generating component contact region and a secondmicrochannel distanced from the intended heat generating componentcontact region; a first fluid inlet opening to the first microchannel; afirst fluid outlet opening from the first microchannel; a second fluidinlet opening to the second microchannel; and a second fluid outletopening from the second microchannel; the first outlet opening beinglarger to allow greater flow therethrough than the second outlet openingsuch that less flow resistance occurs through the first microchannel.10. A method for cooling a heat generating component comprising:providing a fluid heat exchanger including a heat spreader plate; aplurality of microchannels for directing heat transfer fluid over theheat spreader plate, the plurality of microchannels each having a firstend and an opposite end and each of the plurality of microchannelshaving a continuous channel flow path between their first ends and theiropposite ends; a fluid inlet opening for the plurality of microchannelsand positioned between the microchannel first and opposite ends, a firstfluid outlet opening from the plurality of microchannels at each of themicrochannel first ends; and an opposite fluid outlet opening from theplurality of microchannels at each of the microchannel opposite ends;mounting the heat spreader plate onto the heat generating componentcreating a heat generating component contact region where the heatgenerating component contacts the heat spreader plate; introducing aflow of heat exchanging fluid to the fluid heat exchanger; urging theflow of heat exchanging fluid through the fluid inlet into the pluralityof microchannels first to a microchannel region between the ends of theplurality of microchannels; and diverting the flow of heat exchangingfluid into a plurality of subflows that each flow away from the other, afirst of the plurality of subflows flowing from the fluid inlet towardthe first fluid outlet and a second of the plurality of subflows flowingfrom the fluid inlet toward the opposite fluid outlet.
 11. The method ofclaim 10 wherein the fluid inlet is positioned adjacent a central regionof the heat generating component contact region.
 12. The method of claim10 wherein each of the plurality of subflows are substantially half thevolume of the flow.
 13. The method of claim 10 wherein each of the firstof the plurality of subflows passes along the plurality of microchannelsfrom the heat generating component contact region to the microchannelfirst ends.